The present invention relates generally to cardiac pacemakers, and other types of implantable medical devices, which can be programmed and/or analyzed following implantation using an external diagnostic/programmer system. More particularly, the invention relates to an implantable device, diagnostic/programmer, and method wherein software routines automatically evaluate the interaction of the device with a patient""s heart.
Implantable cardiac pacemakers commonly store a variety of different types of diagnostic data which assist the physician in evaluating both the operation of the patient""s heart and the operation of the implanted device. Depending upon the particular pacemaker and its mode of operation, this information may include, for example, a heart rate histogram (which indicates the distribution of the patient""s heart rate over a period of time, such as one month), an event histogram (which indicates the distribution of the various sensing and stimulation events), a sensor indicated rate histogram (which indicates the distribution over time of the recommended pacing rate indicated by an implanted sensor), a variety of event counters, one or more event-triggered intracardiac electrograms, and the status of the pacemaker""s battery.
The various items of diagnostic data may be retrieved from the pacemaker for display and evaluation using a pacemaker programmer/diagnostic system (xe2x80x9cprogrammerxe2x80x9d), which uses RF telemetry to communicate with the implanted device. This is typically accomplished during routine follow-up visits of the patient to the clinic, during which time the patient is asked to hold a telemetry wand in the locality of the implanted pacemaker. To read out and view a particular item of information (e.g., a heart rate histogram), the physician employs a user interface of the programmer to designate the diagnostic item to be retrieved, and then initiates the retrieval. The programmer in-turn interrogates the pacemaker to cause the pacemaker to transmit the selected diagnostic item, and then receives and displays the selected item on the screen. The physician may also initiate various types of tests using the programmer, such as a ventricular or atrial capture test which determines the minimum output (e.g. pulse voltage) needed to effectively stimulate the respective chamber of the heart. The physician may retrieve and adjust various programmable pacing parameters, such as sensor control parameters that are used to adjust the pacing rate according to the output of an event (or other) sensor which detects a signal other than the electrical activity generated within the cardiac tissue and uses this other signal as a guide to the appropriate heart rate.
During the follow-up visit, it is common for the physician (or other support personnel) to follow a predetermined sequence or xe2x80x9cprotocolxe2x80x9d for the evaluation of the patient. The particular protocol will often vary from physician-to-physician and/or clinic-to-clinic, and may be further modified depending upon the medical condition of the patient. By way of example, a follow-up protocol may include the steps of:
(1) retrieving, viewing and printing the atrial and ventricular and/or heart rate histograms;
(2) retrieving and viewing (and optionally printing) the event histogram;
(3) conducting ventricular and atrial sense tests;
(4) conducting ventricular and atrial capture tests; (5) contingent upon the results of steps 1-4, retrieving and viewing the R-wave and P-wave histograms (indicative of the depolarization of the ventricles and the atria, respectively);
(6) retrieving, viewing and printing the sensor indicated rate histogram; and
(7) if appropriate, adjusting the sensor control parameters. During each step of the protocol, the physician typically interviews the patient and records the patient""s comments. At the end of the examination, the physician normally programs the pacemaker to parameters that are appropriate for the patient based on this evaluation (pacemaker prescription) and prepares a written report, which typically includes various printouts of the retrieved diagnostic and test data.
One problem with current diagnostic methods used to evaluate the follow-up patient is that the physician is typically required to scroll through large volumes of data on the programmer screen, even though only selected portions of this data are significant for diagnostic purposes. This is true, for example, in the case of atrial and ventricular capture tests, in which the physician is typically presented with a snap-shot of real-time data (typically, several seconds long), and must scroll through the data to locate the point at which capture was lost. Because much of the data viewed by the physician is not applicable to the final result, the process tends to be inefficient.
Based upon the results of the pacemaker diagnostic evaluation, the physician sometimes alters the pacemaker parameters (i.e., the stored values that specify the therapy delivered by the pacemaker). These modifications to the pacemaker parameters are typically standard given a certain set of results. However, the steps of performing the assessment of capture and sensing thresholds, sensor function and other behavioral characteristics of the pacemaker that may require programming multiple different parameters for each test tend to be time consuming, further adding to the overall time required to complete the follow-up examination. In some cases, because of the relative complexity and the amount of time that is required, these tests are not performed to the potential detriment of the patient.
Many conventional pacemaker diagnostic systems merely provide historical data to the physician and are not capable of providing for real-time analysis of pacemaker capture and sensing thresholds as well as other functional settings. Even those systems which do provide real-time analysis of some diagnostic items often do not allow the clinician or the programmer to modify pacemaker parameters xe2x80x9con the flyxe2x80x9d so that the clinician can immediately observe the results of such parameter modification. This can significantly reduce the physician""s ability to actively interact with the pacemaker to achieve an unambiguous result.
As a patient""s condition may and generally does change over time after receiving an implanted cardiac stimulation device, periodic follow-up testing with the physician is generally performed. These follow-up tests are conducted to evaluate the patient""s natural heart rhythm, physiological cardiac event detection thresholds or pacing capture thresholds, for example. The tests are therefore designed to evaluate and reveal the interaction of the implanted cardiac device and the patient""s heart.
Currently, follow-up tests are performed manually or semi-automatically with external programmers. To that end, the telemetry system of the devices transmits data, such as electrograms and event markers, to the external programmer. The external programmer then, in turn, receives the data and displays the electrograms and event markers along with a simultaneously recorded surface electrocardiogram (ECG). By changing various programmable parameters, such as pacing rates, detection (sensing) settings, stimulation output, and modality with the programmer, and observing the displayed electrocardiogram in conjunction with the simultaneously telemetered electrograms and event markers, the physician is able to discern the interaction of the device with the patient""s heart and make a decision as to whether or not changes in programmed settings are required or the present settings are appropriate for the patient.
Unfortunately, follow-up testing remains both tedious and time consuming for both the patient and the physician. These periodic evaluations may also be performed by physicians without special training in device management, because of a lack of availability of physicians with this expertise. In spite of improvements, there still remains room for human error because the user must still interact with the system to identify, for example, when loss of capture occurs, when loss of sensing occurs, and thus, when to terminate the test for receiving a result from the programmer. If a test is ended at the wrong time, an incorrect result will most likely be obtained. In some systems, the user is allowed the option of selecting a different end-point for the test results once the test has been terminated. While this is a further improvement, many physicians and support staff do not perform the appropriate testing because they are either not knowledgeable, do not want to expend the time, or are confused by various heart rhythms along with the complexity of the pacing system.
Hence, the present invention addresses the need for a fully automated follow-up evaluation procedure. In accordance with the present invention, the event markers are utilized to automatically guide test sequences, when a test is completed and to provide test results with the programmer providing recommendations as to specific programmable parameters. Adoption of the recommended parameters may be left to the physician""s discretion or they may be automatically implemented in the stimulation device. By automating the follow-up evaluation process, consistent and reliable results may be obtained. By allowing these tests to be performed in a totally automatic manner, they are more likely to be utilized at each follow-up visit thus contributing to the improved quality of care that can be provided to the device patient.
The present invention provides an implantable stimulation device, programmer, and method for automatically evaluating the interaction of the device and a patient""s heart. The automatic evaluation procedure may be implemented by the programmer in conjunction with the device or may be implemented by the implantable device itself to make periodic measurements for tracking and automatic adjustment purposes.
The evaluation process responds to event markers generated by the device, representing applied stimulation pulses and sensed physiological cardiac events, to define automated evaluation process sequences, to determine completion of an evaluation procedure, and to determine final evaluation results. The final evaluation results may be visualized on a programmer display and may include recommended changes to the programmable parameters. The recommended settings of the programmable parameters may also be automatically implemented within the device.
The automated evaluation procedure is preferably controlled by a processor within the programmer, or the stimulation device. The processor is preferably configured to analyze the event markers and then automatically adjust the programmable parameters in response to the event markers in accordance with the automated evaluation procedure, and to determine final evaluation results upon completion of the evaluation procedure.
The implantable stimulation device and programmer communicate via a telemetry system. When the automatic evaluation process is implemented by the programmer, the programmer sends appropriate commands to the device responsive to the event markers received from the device. When the automatic evaluation or test procedure is completed, the final evaluation results are determined by the programmer and displayed.
When the automatic evaluation procedure is implemented by the device, the device determines the final evaluation results upon completion and transmits them to the programmer for display.
The automated evaluation procedure of the invention is particularly suited for determining atrial and ventricular sensing thresholds, atrial and ventricular capture thresholds, retrograde conduction times and the propensity to pacemaker mediated tachycardia.